This invention relates to a fluid-pressure-operated, double-acting working cylinder having a piston-dampening arrangement which effects the final braking of a piston within the working cylinder. More specifically, this invention relates to such a working cylinder having a piston-dampening arrangement which effects an accurate positioning of the output shaft utilizing a small amount of fluid pressure relative to the mass of the object which is to be positioned.
Typically, working cylinders which have dampened the final braking operation of the piston have done so only at the end positions of the piston, and have utilized an obstruction-type dampening at the ends of the cylinder, which obstruction dampening impedes the final movement of the piston. Such an arrangement has the disadvantage that the piston braking operation can only be dampened in the end positions and not in any desired intermediate position.
On working cylinders which are used as so-called "positioning" cylinders, however, it is necessary to be able to maintain the work piston in a desired intermediate position. For the positioning of a work cylinder, in other words, the retention of the working piston in any desired intermediate position, a braking arrangement disclosed in U.S. Pat. No. 4,073,217 can be used. On this braking arrangement, the working piston has, on its outer surface, a wedge-shaped activator which can be activated by pressure medium for radially moving braking elements which can be brought into a friction-tight connection with the inside wall of the cy1inder. This approach, however, has the disadvantage that, when the working piston and the objects to be positioned or moved, have a large mass, a rapid braking without a dampening arrangement can only be accomplished by means of special design measures and control mechanisms. Specifically, on such devices, it is not possible to arrive at the desired adjustable position with the necessary precision, accuracy, and ability to repeatedly reproduce identical results.